The use of anionic, cationic and neutral micelles in aqueous solution is being used to serve as a solubilizate for heme and hemin of potoporphyrin IX. The use of the micelles provides membrane-like environments with substantial hydrophobicity for the porphyrins which occupy a position within the micelles. Porphyrin monomers are produced from dimers in the presence of the micelles. Spectra, kinetic and thermodynamic properties of the porphyrins with a variety of biologically important nucleophiles has been investigated. The binding of carbon monoxide from both a kinetic and thermodynamic aspect has been investigated as a function of the micellar charge, and structural relationships between the micelle and its heme. Cynate and imidazole binding has also been investigated. Studies with the model hemoproteins are being directed along lines parallel to those of the native systems in an effort to gain insight into the role the protein (prosthetic group environment) plays in modulating the heme and hemin reactivity. The binding reactions occur on time scales as fast as 10 microseconds. Temperature-jump, stopped-flow and NMR instrumentation are currently being used to investigate and measure the fast reactions.